Effect of Precooking Methods and Storage on Nutrient Composition and Protein Quality in Canned Tuna (Thunnus alalunga)

The modifications in nutrient composition, amino acid content and protein quality of white tuna (Thunnus alalunga) preserves after each of the thermal treatments involved in the canning process was studied. The influence of room temperature on the nutritional quality of canned tuna was also studied during a three year storage period. The biological assays for the study of the protein utilization were carried out on Wistar rats, fed on semi-synthetic diets for 12 days varying only the protein source, casein. or tuna provided which is as follows: raw, cooked in brine, steamed, sterilized tuna, and canned tuna stored for three years. The sterilization process and storage time led to a significant increase in the lipid content of the canned tuna and to a decrease in protein and moisture contents. Amino acid composition of canned and cooked tuna did not show significant changes compared to raw tuna. Neither protein digestibility nor biological value of the cooked, canned and stored tuna showed any deterioration. The protein quality of white tuna meat preserves has been compared with preserves made up of red and white tuna meat.